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| Science Forum Index » Electronics - Design Forum » OT convention of tolerance limits... |
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| RHRRC... |
 Posted: Mon Nov 02, 2009 3:08 pm |
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Guest
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Not an electronics question but after some time googling I have got
nowhere.
question:
In a (mechanical) drawing, if a linear dimension is not given a specific
tolerance what is the convention for the tolerance - as say under the old BS
380.
I think it was that if the number was written as (say) 34 then the tolerance
is +/-1, if the number was written as34.0 it is +/- 0.25, and if it is
written 34.00 the tolerance is 0.015 or something like.
Does anyone know for sure ?
Thanks in advance |
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| Tim Shoppa... |
| Posted: Mon Nov 02, 2009 3:08 pm |
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Guest
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On Nov 2, 12:08 pm, "RHRRC" <h.le... at (no spam) connect-2.co.uk> wrote:
[quote]Not an electronics question but after some time googling I have got
nowhere.
question:
In a (mechanical) drawing, if a linear dimension is not given a specific
tolerance what is the convention for the tolerance - as say under the old BS
380.
I think it was that if the number was written as (say) 34 then the tolerance
is +/-1, if the number was written as34.0 it is +/- 0.25, and if it is
written 34.00 the tolerance is 0.015 or something like.
Does anyone know for sure ?
[/quote]
Reminds me of the tiny Stonehenge in Spinal Tap :-)
Tim. |
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| ChrisQ... |
| Posted: Mon Nov 02, 2009 5:48 pm |
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Guest
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RHRRC wrote:
[quote]Not an electronics question but after some time googling I have got
nowhere.
question:
In a (mechanical) drawing, if a linear dimension is not given a specific
tolerance what is the convention for the tolerance - as say under the old BS
380.
I think it was that if the number was written as (say) 34 then the tolerance
is +/-1, if the number was written as34.0 it is +/- 0.25, and if it is
written 34.00 the tolerance is 0.015 or something like.
Does anyone know for sure ?
Thanks in advance
[/quote]
If you are talking inches, iirc, the BS drawing standards specified +/-
0.025", where tolerances are not specified at all, and 0.010", 0.005"
was common for everything else. If you are down to 001", then it's a
precision ground item usually, as it's difficult to hand turn to that
accuracy in production. Modern cnc auto's might be able to do it though...
Regards,
Chris |
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| JosephKK... |
| Posted: Mon Nov 09, 2009 5:22 am |
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Guest
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On Mon, 2 Nov 2009 20:08:43 -0000, "RHRRC" <h.lewis at (no spam) connect-2.co.uk>
wrote:
[quote]Not an electronics question but after some time googling I have got
nowhere.
question:
In a (mechanical) drawing, if a linear dimension is not given a specific
tolerance what is the convention for the tolerance - as say under the old BS
380.
I think it was that if the number was written as (say) 34 then the tolerance
is +/-1, if the number was written as34.0 it is +/- 0.25, and if it is
written 34.00 the tolerance is 0.015 or something like.
Does anyone know for sure ?
Thanks in advance
[/quote]
Canonically it is +/- 1 in the least significant digit.
thus:
43000 gets +/- 1000
380 gets +/- 10
34 gets +/- 1
18.0 gets +/- 0.1
and
50.00 or 54.13 gets +/- 0.01
From high school science 'bout 40 years ago. |
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